Turkey-red oil.

The Textile Mercury, 12.3.1892

De Milly was one of the the first who, several years ago, succeeded in the industrial saponification of fats and oils by means of steam. The operation had been tried in laboratories and partially succeeded, but before De Milly the decomposition was not nearly so complete as when working on the large scale. De Milly overcame these difficulties in a very ingenious manner, the principal difficulty to be contended with being the treatment of the mixture containing the fatty matter and the water. The author has utilised De Milly's process for the preparation of sulpho-ricinoleic acid, or, rather, ricinolcic acid.

The chief advantage consists in the possibility of utilising the glycerine, and doing away with the washings, which always cause a loss of a certain qaantity of matter; another advantage is the doing away with the sulphuric acid. According to the experience of the author, it is sufficient to imperfectly saturate the ricinolcic acid with soda, to obtain aprodtiot which gives every satisfaction. Thus, a mixture of fatty acid with a quantity of caustic aoda, corresponding to 2-5% of anhydrous soda, gives a very acid soap, which is precisely the body suitable for Turkey-red dyeing. The contents of the above paper give an indication of the subject the author has in view in trying to obtain ricinoleic acid by the decomposition of castor oil by means of steam. He did not however, fail to observe that it was not normal richroleic acid which be obtained by this process, but an acid having, from a chemical as well as from a tinctorial point of view, different properties from those of the normal acid. The diminution in the capacity of saturation was the evident indication of a molecular condensation. On titratiog with ammonia, using phenolphthalein as indicator, the titration of the normal acid took place with precision. That of the ricinoleic acid, condensed or polymerised, took place properly as lone as the polymerisation did not pass beyond di-ricinoleic acid; but in going further the acid properties of the fatty body tended to become weaker. The addition of ammonia produces solutions which become more and more milky, whilst the normal acid and those acids the molecular weights of which are not too high, give perfectly clear solutions with ammonia.

The fatty acid resulting from the saponification of castor oil by water, at St. Denis, in the July of 1889, bad the following properties:—Its capacity of saturation was in the proportion of 27, against 44 of the normal acid; and its molecular weight 480, against 298, that of the normal acid. The tone of alizarine pink was bluer with polymerised acid than with the normal. On sulphonating it, the compound obtained gives a yellower shade than the unsulphonated one: it is, in other words, the same as the normal acid, the sulphonated derivative of which gives a yellower shade than the normal acid.

Generally speaking, the following are the results of the author's researches: — The product obtained by the introduction of the sulphonic group gives a yellower brightening effect than the unsulphonated acid. The polymerisation of the acid gives a bluer brightening effect than the normal acid. The treatment with sulphuric acid has the effect, not only of introducing the sulphonic group iuto the ricinoleic molecule, but of polymerising that acid. The same reactions are obtained when treating castor oilwith sulphuric acid sulphonation and polymerisation take place.

It is to be supposed that when the sulphuric acid has combined with either the fatty acid or with the castor oil, a sulpho-ricinoleic acid, sulphonated and polymerised, is formed. The action of the water has the effect of partially decomposing it, in proportions which vary according to the quantity of the water used for washing and the temperature.

It is for this reason that oil for red contains a sulpho-poly-ricinoleie acid, soluble in water, holding in solution poly-ricinoleic acids insoluble in water, but dissolved by the former, and not containing any sulphonated compound. One could confirm these facts by adding to the sulphonated acid a certain quantity of pure fatty acid, free from unsulphonated bodies, "which have been extracted by means of ether." The solution thus obtained, hydrated by a mixture of water in any desired proportions, reproduce Turkey-red oil; this is, in fact, a synthesis of Turkey-red oil.

The author has already observed that this sulphonated derivatives, the acid properties of which are more distinct than those of the unsulphonated bodies, can be titrated by using litmus as indicator, whilst the unsulphonated acids give results only with phenolphthalein, which allows one to titrate the two bodies whilst they are together, as in Turkey-red oil.

When one saponifies tbe polymers of ricinolcic acid with soda, they do not undergo any modification. Their soap, precipitated by sulphuric acid, reproduces the polymer unaltered. When, on the contrary, the saponification takes place on prolonged boiling, or, better, in an autoclave, at a temperature above 1000, the normal is reproduced with its general properties. In order to obtain a sulphonated compound, giving a brightening effect as yellow as possible, it is necessary to avoid polymerisation. The ideal would be to have to do with the normal acid sulphonated, whilst one has, in Turkey-red oil, polymers of which the bluish brightening properties partly destroy those of a yellowish brightening effect, owing to the introduction of the sulphuric group into the molecules.